/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.proxydroid;

import java.io.FileDescriptor;

/**
 * Utility methods for creating and managing a subprocess.
 * <p>
 * Note: The native methods access a package-private java.io.FileDescriptor
 * field to get and set the raw Linux file descriptor. This might break if the
 * implementation of java.io.FileDescriptor is changed.
 */

public class Exec {
	static {
		System.loadLibrary("exec");
	}

	/**
	 * Create a subprocess. Differs from java.lang.ProcessBuilder in that a pty
	 * is used to communicate with the subprocess.
	 * <p>
	 * Callers are responsible for calling Exec.close() on the returned file
	 * descriptor.
	 * 
	 * @param cmd
	 *            The command to execute
	 * @param args
	 *            An array of arguments to the command
	 * @param envVars
	 *            An array of strings of the form "VAR=value" to be added to the
	 *            environment of the process
	 * @param processId
	 *            A one-element array to which the process ID of the started
	 *            process will be written.
	 * @return the file descriptor of the started process.
	 * 
	 */
	public static native FileDescriptor createSubprocess(String cmd,
			String[] args, String[] envVars, int[] processId);

	/**
	 * Causes the calling thread to wait for the process associated with the
	 * receiver to finish executing.
	 * 
	 * @return The exit value of the Process being waited on
	 * 
	 */
	public static native int waitFor(int processId);

	/**
	 * Close a given file descriptor.
	 */
	public static native void close(FileDescriptor fd);

	/**
	 * Send SIGHUP to a process group.
	 */
	public static native void hangupProcessGroup(int processId);
}
